PDF Merger

What "merging" a PDF actually does

A PDF is a graph of page objects pointed to by an index called the xref table. Merging isn't concatenation — it's copying every page object from each input PDF into a new output document and rewriting its internal references. That's why the merged PDF is roughly the sum of the inputs in bytes; there's no re-encoding, no quality loss, and no resolution drop. Fonts, images, vector paths, hyperlinks, and form fields carry across intact.

This tool uses pdf-lib, a pure-JavaScript PDF engine. The PDFs you drop onto the page are parsed entirely in your browser, their pages are extracted, a fresh document is assembled in memory, and the result is offered for download as a new file. At no point do the bytes touch a server.

Common reasons to merge

• Collating a set of scanned receipts into a single expense claim.
• Assembling chapters of a thesis into the final submission document.
• Combining an application form with supporting documents before emailing it.
• Joining contract + appendices + signature page into one deliverable.
• Turning a pile of individually-exported invoices into a monthly bundle for accounting.

Things the merge preserves

• Page layout, fonts, and embedded images, exactly.
• Internal hyperlinks that target the same page.
• External hyperlinks.
• Page dimensions — a mix of A4 and Letter pages will come through at their original sizes.
• Embedded text (selectable / searchable).

Things the merge won't carry over

• Bookmarks / outlines are dropped. Re-create them in Acrobat / Preview after the merge if you need chaptering.
• Document-level metadata — author, title, subject — is pulled only from the first PDF.
• Interactive form fields with identical field names across two inputs collide and can behave oddly. Flatten forms first if you merge filled forms.
• Digital signatures are stripped; a signed PDF cannot remain signed after any structural edit, including merging.
• Password-protected PDFs cannot be merged without first being unlocked.

If the output PDF is huge

Merging doesn't shrink files. If the inputs are large (scanned documents often are), the output will be too. The most common culprit is raster scans saved at 300 DPI. If you need a smaller file, run the merged PDF through a PDF compressor that downsamples images, or re-scan at 150 DPI. Don't compress before merging — the merger preserves whatever you give it.

Privacy

Every byte of every PDF you drop here stays in your browser tab. The merge runs via pdf-lib in JavaScript. You can verify this by opening your browser's network panel and watching the merge happen — no outbound requests will fire. That makes the tool appropriate for PDFs containing personal data, contracts, medical records, or anything else you wouldn't want on a stranger's server.